Medicinal antioxidants are compounds that may be used for the prevention of tissue damage induced by lipid peroxidation (Halliwell, B., FASEB J. 1:358-364, 1987). During lipid peroxidation free radicals interact with polyunsaturated fatty acids to form lipid peroxyl radicals, which produce lipid hydroperoxides and further lipid peroxyl radicals. This peroxidative cascade may eventually consume an essential part of the membrane lipid, which may lead to changes in membrane permeability and ultimately in cell death. The peroxidative degradation of lipids also leads to the formation of potentially toxic products such as malondialdehyde.
Numerous recent studies indicate that peroxidation of low density lipoproteins contribute to the formation and progression of atherosclerosis. Various antioxidants have been shown to decrease arterial lesions in animal models of atherosclerosis. So it is believed that the reduction of the atherogenic risk is associated with the reduction of atherogenic lipid peroxides which are essentially transported in the LDL fraction in the serum.
There is evidence that free radical induced lipid peroxidation occurs in ischemic injury, e.g. in cardiac ischemic injury following coronary thrombosis or in reperfusion ischemic injury during surgery. The importance of lipid peroxidation in tissue damage associated with ischemia is supported by the protective effect of natural and synthetic antioxidants or antioxidant enzymes in diverse ischemic models. It is believed that reduction of the lipid peroxidation associated with ischemia protects the vital organs, such as the cardiovascular system and cerebral tissue, from oxidative damage, e.g. in patients recovering from myocardial infarction or during surgery.
NADPH oxidase of polymorphonuclear leucocytes (neutrophils) is the source of superoxide radical anion and other reactive oxygen species which are important in the defence against pathogens. Tissue damage due to the uncontrolled production of reactive oxygen species by activated neutrophils is known to occur in connection with diseases like psoriasis or acute or chronic inflammatory diseases, e.g. inflammatory bowel disease. It is believed that compounds which inhibit the oxidative burst of the activated neutrophils can be of therapeutic interest in the prevention and treatment of these diseases. Furthermore, recent studies indicate that increased oxygen radical production by neutrophils (oxidative stress) is present in HIV-infected patients and that the oxygen radical overproduction can increase the expression and replication of HIV-1 (Jarstrand, C. et al., Chemico-Biological Interactions 91, 141-146, 1994; Schreck, R. et al., The EMBO Journal, 10, 8, 2247-2258, 1991; Favier, A. et al., Chemico-Biological Interactions 91, 165-180, 1994 and Fuchs, J. et al., Medical Hypotheses, 36, 60-64, 1991). Therefore it is believed that compounds which inhibit the oxidative burst of the activated neutrophils can be of therapeutic interest also in the treatment of AIDS.